1. Field of the Invention
The present invention relates to a substrate processing apparatus, and more particularly, to an oxidation or contamination preventing technique for a substrate which is subjected to processing in an air-tightly closed processing chamber and for example, the invention can effectively be utilized for carrying out, for a semiconductor wafer, oxide film forming processing or diffusion processing, anneal processing and film forming processing in a producing process of a semiconductor device.
2. Description of the Related Art
In general, in a producing process of a semiconductor device, a batch-type vertical hot wall-type substrate processing apparatus is widely used for carrying out the oxide film forming processing or the diffusion processing, the anneal processing and the film forming processing for a semiconductor wafer (wafer, hereinafter).
For example, the batch-type vertical-type hot wall-type substrate processing apparatus (heat treatment apparatus, hereinafter) for carrying out heat treatment such as the oxide film forming processing or the diffusion processing, and the anneal processing comprises a vertically disposed process tube for forming a processing chamber into which wafers are to be transferred, a gas introducing port for introducing gas into the processing chamber, a discharge tube for evacuating the processing chamber to produce a vacuum, and a heater disposed outside the process tube for heating the processing chamber. A plurality of wafers are transferred into the processing chamber from a lower end furnace port in a state in which the wafers are concentrically arranged and held by a boat, the processing chamber is heated by the heater, and the heat treatment such as the oxide film forming processing or the diffusion processing, and the anneal processing is carried out.
In the conventional heat treatment apparatus, the wafers before they are transferred into the processing chamber or after they were transferred out from the processing chamber are in contact with atmosphere, and undergo oxidation due to oxygen or moisture included in the atmosphere. Therefore, there is a problem that a not-pre-assumed oxide film (natural oxide film, hereinafter) is uncontrollably formed on the wafer, and precision of processing such as the oxide film forming processing or the diffusion processing, and the anneal processing is lowered.
Thereupon, there has been proposed a heat treatment apparatus comprising a chamber formed with a preliminary chamber in which a boat stays on standby below a process tube, and inert atmosphere is formed in the preliminary chamber. In this heat treatment apparatus, wafers held by the boat which stays in the preliminary chamber on standby before the wafers are transferred into the processing chamber and after the wafers are transferred out from the processing chamber are placed in the inert atmosphere. Therefore, the wafers do not undergo oxidation by oxygen or moisture included in the atmosphere. As a result, an unnecessary oxide film is not formed on the wafer, and the problem that precision of processing is lowered is avoided.
In a heat treatment apparatus having a preliminary chamber forming inert atmosphere, wafers are attached and detached by a wafer transferring apparatus during a standby state of a boat in the preliminary chamber. In this case, if a wafer cassette (cassette, hereinafter) accommodating a plurality of wafers is directly transferred into and out from the preliminary chamber, a large amount of air outside the preliminary chamber is adversely introduced into the preliminary chamber when the cassette is transferred into and out from the preliminary chamber. Therefore, it is necessary to provide another preliminary chamber (cassette chamber, hereinafter) into and out from which the cassette is transferred, separately from the former preliminary chamber in terms of fluid.
However, if the cassette chamber is formed as a so-called load lock preliminary chamber whose cassette chamber is evacuated to produce a vacuum and into which nitrogen gas is charged, there is a problem that the producing cost and running cost are increased. Further, since the cassette has a relatively large volume, a large amount of air outside the cassette chamber is prone to be introduced into the cassette chamber when the cassette is transferred into and out from the cassette chamber. Therefore, in order to maintain low concentration air environment in the cassette chamber, it takes a long time to evacuate the cassette chamber to produce a vacuum, and to charge nitrogen gas, and this deteriorates the throughput of the heat treatment apparatus.
According to a first aspect of the present invention, there is provided a substrate processing apparatus, including:
a process tube which forms a processing chamber provided at its lower end with a furnace port;
a boat which is to go in and out from the processing chamber for transferring a substrate or substrates into and out from the processing chamber;
a first preliminary chamber which is provided at one side of the process tube and which is to be charged with inert gas; and
a substrate transferring apparatus disposed in the first preliminary chamber for transferring the substrate or the substrates between the boat and a cassette which accommodates the substrate or the substrates, wherein
the boat and the cassette are respectively allowed to be inserted into the first preliminary chamber through a lower wall of the first preliminary chamber from below.
According to the substrate processing apparatus according to the first aspect of the present invention, since the cassette is inserted into the preliminary chamber into which the boat is inserted, it is unnecessary to form a special cassette chamber. Further, since the preliminary chamber is formed such that the cassette can be inserted into the preliminary chamber from below, the overflow of inert gas effectively prevents air outside the preliminary chamber from being introduced when the cassette is transferred into and out from the preliminary chamber. Therefore, according to the above measure, it is possible to enhance the processing precision while preventing the producing cost and running cost from being increased, and prevent the throughput from being deteriorated.
According to a second aspect of the present invention, there is provided a substrate processing apparatus, including:
a processing chamber for processing a substrate or substrates;
a substrate supporting member for supporting the substrate or the substrates in the processing chamber;
a preliminary chamber which is to be charged with inert gas; and
a substrate transferring apparatus for transferring, in the preliminary chamber, the substrate or the substrates between the substrate supporting member and a cassette which accommodates the substrate or the substrates, wherein
the cassette is allowed to be inserted into the preliminary chamber through a lower wall of the preliminary chamber from below.
According to a third aspect of the present invention, there is provided a substrate processing apparatus, including:
a preliminary chamber; and
a substrate transferring apparatus disposed in the preliminary chamber for transferring substrate or substrates in and out of a cassette which accommodates the substrate or the substrates, wherein
the cassette is allowed to be inserted into the preliminary chamber through a lower wall of the preliminary chamber from below.